1. Field of the Invention
This invention relates to methods and devices for treating skin conditions using ultrasound.
2. Description of the State of the Art
Acne affects more than 90% of all adolescents, nearly 50% of all adult women and 25% of all adults. One of the main causes of acne is improper drainage of the hair follicle caused by a plug of dead cells or dirt that trap oil and bacteria. The hair follicle opening is approximately 50 μm to about 100 μm in diameter. The opening of any other pore on the skin is substantially smaller. In particular, the opening of a sweat pore is less than about 30 μm in diameter.
There are a variety of ways to treat acne. Benzoyl peroxide is one of the most commonly used ingredients in over-the-counter treatments, and it can be very effective in treating mild cases of non-inflammatory acne. It is safe for children as well as adults, and may be combined with other topical or oral treatments. For patients who suffer from moderate to severe acne, doctors may prescribe a combination of topical remedies and oral antibiotics. The most common oral medications used to treat acne are tetracycline, minocycline, doxycycline and erythromycin.
Alternatives to medication include UV light radiation, laser treatment, or abrasion. Most of these systems are large and in most cases require professional treatment. U.S. Pat. No. 6,635,075 by Li et al. describes a heating device that can also be used to treat acne. The device described in therein uses a heater and temperature sensor to maintain a constant temperature surface that can be applied to skin. In order to prevent burns during the long application time (minutes), the maximum temperature allowed is about 62° C. The long treatment time makes this device impractical for normal acne treatment.
Various ultrasound treatment devices and/or methods for treating tissue have been proposed as discussed in U.S. Pat. No. 6,692,450 to Coleman, U.S. Pat. No. 6,325,769 to Klopotek and references therein. These systems generally use low frequency ultrasound where coupling layers or focusing elements can be placed between the transducer and skin. The use of low frequency ultrasound (<5 MHz) results in deep penetration which is not suitable for treating acne. In addition, these ultrasound systems operate in a linear mode which requires very thin piezoelectric elements which make them delicate and impractical for hand held consumer devices. A need exists for a compact device that can be used effectively and quickly to treat acne. The present invention fulfills this need, and further provides related advantages.
Methods of rejuvenating skin range from the aggressive face lift surgery and skin resurfacing by lasers (for example, using CO2 lasers) or chemical peel, to the less effective non-ablative lasers systems, and RF energy skin rejuvenation systems, microdermabrasion, the use of abrasive devices as well as various lotions and creams. Additional alternative methods include UV, infrared and light radiation, laser treatment, mechanical abrasion or ultrasound energy. Most of these systems are large and in most cases require professional treatment. A need exists for effective skin rejuvenation devices.